Embodiments of the invention relate generally to electric drive systems including hybrid and electric vehicles and, more particularly, to charging energy storage devices of an electric vehicle using a multiport energy management system.
Hybrid electric vehicles may combine an internal combustion engine and an electric motor powered by an energy storage device, such as a traction battery, to propel the vehicle. Such a combination may increase overall fuel efficiency by enabling the combustion engine and the electric motor to each operate in respective ranges of increased efficiency. Electric motors, for example, may be efficient at accelerating from a standing start, while internal combustion engines (ICEs) may be efficient during sustained periods of constant engine operation, such as in highway driving. Having an electric motor to boost initial acceleration allows combustion engines in hybrid vehicles to be smaller and more fuel efficient.
Purely electric vehicles use stored electrical energy to power an electric motor, which propels the vehicle and may also operate auxiliary drives. Purely electric vehicles may use one or more sources of stored electrical energy. For example, a first source of stored electrical energy may be used to provide longer-lasting energy (such as a low-voltage battery) while a second source of stored electrical energy may be used to provide higher-power energy for, for example, acceleration (such as a high-voltage battery or an ultracapacitor).
Plug-in electric vehicles, whether of the hybrid electric type or of the purely electric type, are configured to use electrical energy from an external source to recharge the energy storage devices. Such vehicles may include on-road and off-road vehicles, golf carts, neighborhood electric vehicles, forklifts, and utility trucks as examples. These vehicles may use either off-board stationary battery chargers, on-board battery chargers, or a combination of off-board stationary battery chargers and on-board battery chargers to transfer electrical energy from a utility grid or renewable energy source to the vehicle's on-board traction battery. Plug-in vehicles may include circuitry and connections to facilitate the recharging of the traction battery from the utility grid or other external source, for example.
Battery chargers are important components in the development of electric vehicles (EVs). Historically, two types of chargers for EV application are known. One is a standalone type where functionality and style can be compared to a gas station to perform rapid charging. The other is an on-board type, which would be used for slower C-rate charging from a conventional household outlet. EVs typically include energy storage devices such as low voltage batteries (for range and cruising, for example), high voltage batteries (for boost and acceleration, for example), and ultracapacitors (for boost and acceleration, for example), to name a few. Because these energy storage devices operate under different voltages and are charged differently from one another, typically each storage device includes its own unique charging system. This can lead to multiple components and charging systems because the storage devices typically cannot be charged using charging systems for other storage devices. In other words, a charging device used to charge a low-voltage battery typically cannot be used to charge an ultracapacitor or a high-voltage battery.
The effect (i.e., many devices) is generally compounded when considering that in some applications it is desirable to rapidly charge the storage devices using a “gas station” type charging system, while in other applications it is desirable to slow-charge the storage device using a conventional household outlet. However, when multiple energy storage devices of an EV needs charging, such as power batteries, energy batteries, and ultracapacitors, often they do not need the same amount of recharging. For instance, one energy storage device may be nearly or fully depleted and have nearly zero state-of-charge (SOC) while another, at the same time, may be only partially depleted and have a much greater SOC. Or, energy storage devices often comprise a pack or bank of storage cells that can become unbalanced in their amount of energy stored therein. And, as known in the art, the devices typically have vastly different storage capacities, and different operating voltages from one another, as examples.
As such, during a re-charging session of all devices of an EV, re-charging the devices may be inefficient and needlessly time-consuming, overall, because one device may be preferentially charged much quicker to a full state-of-charge (SOC) while another device is charged and reaches its full SOC in a much longer time period.
It would therefore be desirable to provide an apparatus to reduce the overall recharge time for multiple energy storage devices of an EV.